Since the surprising discovery in the late 1980's that retinal cells can be safely transplanted into the subretinal space of mammals, and that this could have potential benefit, and the pioneering work by the present inventor and colleagues beginning in mid-1990's that such transplants could also be safely delivered into humans, there has been an ever-increasing interest in devices and methods for implanting materials into the back of the eye. Recent, widely publicized human studies involving implantation of phototransducing devices into patients having retinal diseases have added further to the demand for and interest in devices and methodologies for implanting materials into the eye, and in particular devices and methodologies for epiretinal and subretinal implantation. Subretinal implantation refers to implanting materials beneath the retina, for example between the retina and the choroid or between the retina and the retinal pigment epithelium (RPE). Epiretinal implantation refers to implanting materials into the eye on top of the retina or close thereto, and also includes attachment thereof to the upper surface of the retina.
There are a variety of references know to those skill in the art that address ophthalmic pathologies. There are very limited, currently available treatments for retinal pathologies. However, one of ordinary skill in the art will be familiar with publications disclosing methods and apparatuses for conducting related research, and methods, instruments, and implantable materials and devices for treatment and/or proposed treatment of ophthalmic diseases and injuries. Specifically incorporated by reference as if reproduced in full below are U.S. Pat. No. 6,514,238, entitled Method For Preparation And Transplantation Of Volute Grafts And Surgical Instrument Therefor, U.S. Pat. No. 6,045,791, entitled Retinal Pigment Epithelium Transplantation, U.S. Pat. No. 6,036,678, entitled Method For Preparation And Transplantation Of Planar Implants And Surgical Instrument Therefor, U.S. Pat. No. 5,962,027, Retinal Cell Transplant, U.S. Pat. No. 5,868,728, entitled Medical Linear Actuator For Surgical Delivery, Manipulation, And Extraction, U.S. Pat. No. 5,817,075, entitled Method for preparation and transplantation of planar implants and surgical instrument therefore, Vaughan, Daniel, et al., General Ophthalmology, Appleton & Lange (1999), and Kaplan et al., “Human Photoreceptor Transplantation in Retinitis Pigmentosa, A Safety Study,” Archives of Ophthalmology, 115:1168–1171 (1997).
The foregoing patents disclose inter alia devices for ophthalmic implantation of solid and semisolid implants. In particular, devices are disclosed that utilize a plunger-in-tube arrangement, wherein the plunger may extend substantially to or beyond an opening in the tip of a cannula inserted into an eye to express material contained therein by (1) direct physical contact between the plunger distal end and the implant, or (2) via direct physical contact between a solid or semisolid bumper driven by direct physical contact with the plunger distal end. Such “direct drive” devices are desirable due to the high level of control over the implant delivery speed, with minimal deviations due to temperature variations or hysteresis. Also disclosed is the desirability of using a fluid or hydraulic “bumper” between the distal end of the plunger and the implant, but a means for accomplishing this was not disclosed.
Use of a solid plunger has been found in some instances to lead to damage to the implant. In some instances, the implant composition sticks to the interior of the delivery cannula, making it desirable to surround the implant with a lubricant or carrier solution. However, an implantation device did not exist wherein the implant could be readily loaded into the device with an appropriate carrier or lubricant solution, and delivered with a high degree of control, such as the high degree of control needed for subretinal implantation. Excessive flow or pressure could detach or damage the retinal or other eye structures, whereas insufficient pressure or flow will not express the implant. Excessive size of the delivery opening could lead to leakage of carrier fluid and a loss of control, but insufficient size of the delivery opening can cause an excessive focused fluid flow pressure, prevent expression of the implant, or damage the implant upon expression.
Thus, there remains a need for an implantation device, particularly an implantation device for use in ophthalmic implantation, wherein the implant can be delivered in a fluid carrier, as well as methods for fabrication, loading, and use thereof.